1. Field of the Invention PA1 2. Description of the Related Art
The present invention relates to an optical apparatus for controlling the movement of a zoom lens.
Hitherto, zoom lenses (hereinafter referred to as a constant magnification zoom) have been proposed, having a driving means (hereinafter also referred to as an actuator) for electrically driving a zoom lens when the driving means detects that a photographer is operating an operation member, or for concurrently detecting the position of a focusing lens with an autofocus mechanism to automatically drive a zoom lens so that a constant photographic magnification is attained. Also, various zoom optical systems having a focusing function for focusing on a close object, i.e., a so-called macro function, provided use optical elements other than a focusing lens, have already been designed.
Of such zoom optical systems, when a macro function starting from an end point of a zooming range of a magnification or compensation lens is used, a macro focus function can be made integral with the zoom mechanism (e.g., an arrangement in which a cam curve for the closest photographic area is formed on the extension line of the cam curve in the zoom photographic area of a cam member for controlling the movement of the optical system for varying the zoom lens barrel). Therefore, it is possible to prevent the mechanical arrangement from becoming complex and to easily change from a zooming to a macro photographing mode.
However, in the example of the prior art, when an object to be autofocused comes extremely close or moves farther away after the magnification has been determined in a constant magnification zoom mode or the like, an unnatural photograph is obtained because the zooming lens is driven to a wide-angle/telephoto side according to the distance of the object so as to attain a constant magnification. Depending upon the brightness of the object, since the lens is driven to the telephoto position as the object moves away, the lens position may go beyond the camera shake limit or the illuminating angle of the strobe. In the recent trend for higher zoom ratios, the higher the magnification of the zooming lens, the greater the tendency to go beyond these limits.
Regarding macro-photographing, when a camera lens capable of photographing at the closest distance is applied to the autofocus (AF) lens, since only an actuator for driving a focusing lens is installed in an AF lens, the member for operating the zooming lens must be manually operated in the macro area in order to perform focusing, though AF is possible in an ordinary photographic area. Hence, complete AF cannot be attained.
Recently, an arrangement has been proposed in which an actuator for driving a zooming lens is installed, and the zooming lens is moved automatically to a desired focal length, or the movement of the focusing lens is detected and a constant magnification is attained. However, there is the problem that the actuator only controls the focal length when driving the zooming lens.